The Battery’s Role

Much of the electronic equipment in use today requires some type of self-contained reserve power

Lead-acid batteries were invented in 1859 by French physicist Gaston Planté and are the oldest type of rechargeable battery. Despite having a very low energy- to-weight ratio and a low energy-to-volume ratio, its ability to supply high surge currents means that the cells maintain a relatively large power-to-weight ratio. This type battery does tend to degrade with age and should be replaced prior to the capacity dropping below required minimums.

Lithium-ion battery

Lithium-ion batteries are common in much of today’s electronics with one of the best energy-to-weight ratios, no memory effect, and a slow loss of charge when not in use. Beyond consumer electronics this type battery is growing in popularity for aerospace applications due to their high energy density. Research is yielding a stream of improvements in technology, focusing on energy density, durability, cost, and safety.

Shelf life can be considered a disadvantage in certain lithium batteries. Over time, the cell’s capacity diminishes as the increase in internal resistance reduces the ability to deliver current and is more pronounced in high demand applications. The decrease means that older batteries do not charge as much as new ones and therefore capacity is decreased.

In January 2008, the U.S. Department of Transportation ruled that passengers on board commercial aircraft could carry lithium batteries in their checked baggage if the batteries are installed in a device. Types of batteries affected by this rule are those containing lithium, including Li-ion, lithium polymer, and lithium cobalt oxide chemistries. Lithium-ion batteries containing more than 25 grams (0.88 ounces) equivalent lithium content (ELC) are exempt from the rule and are forbidden in air travel. This restriction greatly reduces the chances of the batteries short-circuiting and causing a fire.

Additionally, a limited number of replacement batteries may be transported in carry-on luggage. Such batteries must be sealed in their original protective packaging or in individual containers or plastic bags.

Some shipping agents restrict air shipping of lithium and lithium-ion batteries, and products containing them.

Nickel-cadmium battery

The nickel-cadmium battery (commonly abbreviated NiCd or NiCad) is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes.

The abbreviation NiCad is a registered trademark of SAFT Corporation, although this brand name is commonly used to describe all nickel-cadmium batteries. The abbreviation NiCd is derived from the chemical symbols of nickel (Ni) and cadmium (Cd).

There are two types of NiCd batteries: sealed and vented.

Sealed NiCd cells may be used individually, or assembled into battery packs containing two or more cells. When NiCds are substituted for other battery types, the lower terminal voltage and smaller ampere-hour capacity may reduce performance and this should be considered prior to any substitution. Miniature cells find their way into devices with computer-memory requirements along with many consumer electronics.

Specialty NiCd batteries are used in cordless and wireless telephones, emergency lighting, and other applications. With a relatively low internal resistance, a NiCd battery can supply high surge currents. This makes them a favorable choice for remote-controlled devices, as well as cordless power tools. Larger wet cells are used for main aircraft batteries, electric vehicles, and standby power.

Nickel-cadmium cells have a nominal cell potential of 1.2 volts. This is lower than the 1.5 volts of alkaline and zinc-carbon primary cells, and consequently they are not appropriate as a replacement in all applications. However, the 1.5 volts of a primary alkaline battery refers to its initial, rather than average, voltage. Unlike alkaline and zinc-carbon primary cells, a NiCd cell’s terminal voltage only changes a little as it discharges. Because many electronic devices are designed to work with primary cells that may discharge to as low as 0.90 to 1.0 volts per cell, the relatively steady 1.2 volts of a NiCd is enough to allow operation.

Recently, nickel-metal hydride (Ni-MH) and lithium-ion batteries (Li-ion) have become commercially available and less costly. Where energy density is important, Ni-Cd batteries are now at a disadvantage compared to Ni-MH and Li-ion batteries. However, the Ni-Cd battery is still very effective in situations requiring very high discharge rates as the Ni-Cd can endure such discharge with no damage or loss of capacity. Recharging prior to a complete drain can have a negative impact on this type battery as it tends to have a memory.

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